METHOD FOR CLEANING ELECTROPHORETIC COATING BATHS, AND DEVICE THEREFOR

Abstract

Described herein is a method for cleaning an electrocoating bath in a continuous facility, where a skid connected to a conveying installation is conveyed through the electrocoating bath, and where the skid includes a filter medium; the filter medium is secured on the skid via at least one movable connecting element; the movable connecting element allows the orientation of the filter medium at the interface between electrocoating bath and air; and, after immersion of the skid into the electrocoating bath, during the conveying of the skid through the electrocoating bath, the filter medium is oriented at the interface between electrocoating bath and air and is drawn along the surface of the electrocoating bath. Also described herein is a skid for use in the cleaning method.

Claims

1. A method for cleaning an electrocoating bath in a continuous facility, where a skid connected to a conveying installation is conveyed through the electrocoating bath, and wherein (a) the skid comprises a filter medium, (b) the filter medium is secured on the skid via at least one movable connecting element, (c) the movable connecting element allows the orientation of the filter medium at the interface between electrocoating bath and air, and (d) after immersion of the skid into the electrocoating bath, during the conveying of the skid through the electrocoating bath, the filter medium is oriented at the interface between electrocoating bath and air and is drawn along the surface of the electrocoating bath.

2. The method as claimed in claim 1, wherein the skid comprises one or more buoyancy elements secured on the filter medium and/or connecting element; and/or the connecting element between filter medium and skid conveys the filter medium onto the surface of the electrocoating bath by means of a drive; and/or the filter medium acts as a buoyancy body due of its density or enclosed cavities.

3. The method as claimed in claim 1, wherein the skid comprises one or more additional filter inserts and/or a measuring apparatus.

4. The method as claimed in claim 1, wherein the filter medium comprises one or more water-repelling polymers.

5. The method as claimed in claim 4, wherein the water-repelling polymer or polymers are selected from the group consisting of polyalkylenes.

6. The method as claimed in claim 1, wherein the filter medium is disposed substantially perpendicularly to the conveying direction of the skid on the surface of the electrocoating bath and/or the filter medium occupies at least 80% of the width of the dipcoating tank.

7. The method as claimed in claim 1, wherein the filter medium is selected in the form of a sheetlike textile product selected from the group consisting of woven fabrics, knitted fabrics, felts and nonwovens.

8. The method as claimed in claim 1, wherein the filter medium physisorbs or chemisorbs substances which have accumulated at the surface of the electrocoating bath and/or which possess a surface tension of less than 35 mN/m.

9. The method as claimed in claim 3, wherein the additional filter insert or inserts comprise materials selected from the group consisting of water-repelling polymers, and are present in housings, nets and/or bags that are pervious to the electrocoating material but not pervious to the filter materials.

10. The method as claimed in claim 3, wherein the measuring apparatus serves to analyze the constitution of the electrocoating bath and/or verifies the effectiveness of the cleaning method.

11. A skid for continuous electrocoating facilities, the skid comprising a filter medium which is connected to the skid via one or more movable connecting elements in such a way that during operation of the continuous electrocoating facility the filter medium is able to adopt an orientation at the interface between electrocoating bath and air.

12. The skid as claimed in claim 11, wherein the skid comprises one or more buoyancy elements secured on the filter medium and/or connecting element.

13. The skid as claimed in claim 11, wherein the skid comprises one or more additional filter inserts and/or a measuring apparatus.

14. The skid as claimed in claim 11, wherein the filter medium and, where present, the additional filter inserts comprise materials which are selected from the group consisting of water-repelling polymers.

15. The skid as claimed in claim 13, wherein the measuring apparatus serves to analyze the constitution of the electrocoating bath and/or verifies the effectiveness of the cleaning method.

Description

[0053] FIG. 1 shows the diagram of a continuous-travel electrocoating facility in pendulum conveying mode. The skids (1) in the immersion zone (E) and the emergence zone (A) of the electrocoating bath comprise the filter medium (2) in the folded-in state, the optional additional filter units (5), and an optional measuring apparatus (6). The middle skid (1), which is fully immersed in the electrocoating bath, shows the filter medium (2) in the folded-out state, and the optional additional filter units (5) and also an optional measuring apparatus (6) in the fully immersed state. The arrow indicates the conveying direction.

[0054] FIG. 2 shows the diagram of a continuous-travel electrocoating facility in overhead conveying mode. The skids (1) in the immersion zone (E) and the emergence zone (A) of the electrocoating bath comprise the filter medium (2) in the folded-in state, the optional additional filter units (5), and an optional measuring apparatus (6). The two middle skids (1), which are fully immersed in the electrocoating bath, show the filter medium (2) in the folded-out state, and the optional additional filter units (5) and also an optional measuring apparatus (6) in the fully immersed state. The arrow indicates the conveying direction.

[0055] FIG. 3A, in a side view, shows the diagram of a skid (1) of the invention equipped with a folded-in filter medium (2), the optional additional filter inserts (5), and an optional measuring apparatus (6).

[0056] FIG. 3B, in a side view, shows the diagram of a skid (1) of the invention equipped with a folded-out filter medium (2), the optional additional filter inserts (5), and an optional measuring apparatus (6).

[0057] FIG. 4 shows the diagram of a skid (1) of the invention from above, equipped with a filter medium (2), the optional additional filter inserts (5), and an optional measuring apparatus (6).

[0058] The method of the invention has been found to be extremely effective and it has been possible to observe cleaning or decontamination of the electrocoating bath that goes well beyond the cleaning of the bulk phase of the electrocoating bath, by the binding of disruptive substances to the filter medium (2). In particular, after the implementation of cleaning of a contaminated electrocoating bath, the metal panels coated in the electrodeposition coating process exhibited a significantly lower number of surface defects, and especially a lower number of craters. In this way it was also possible to prevent the premature replacement of the electrocoating bath and also to prevent prolonged interruption to the coating process of the kind inevitably associated with such replacement.

LIST OF REFERENCE SIGNS

[0059] (1) skid

[0060] (2) filter medium

[0061] (3) connecting element

[0062] (4) buoyancy element

[0063] (5) additional filter inserts

[0064] (6) optional measuring apparatus

[0065] (A) emergence zone

[0066] (E) immersion zone